In the past, in a chain having a hollow roller housing cylindrical rollers therein used as a conveyor chain, a number of cylindrical rollers are disposed with peripheral surfaces circumscribed each other between the outer peripheral surface of a bushing fitted over a connecting pin and the inner peripheral surface of the roller, and the outer peripheral surface of the roller is slightly projected from an upper side and a lower side of a chain link, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-78523.
In the above-described conventional conveyor chain, a number of cylindrical rollers 3 circumscribe on the outer peripheral surface of a bushing 1 and inscribe the inner peripheral surface of a hollow roller 2 for rolling while engaging each other, as shown in FIG. 4. When the hollow roller 2 rotates clockwise relative to the bushing 1 in a direction of arrow, the respective cylindrical rollers roll clockwise. Therefore, in the peripheral surface portion in which the cylindrical rollers 3 engage the adjacent rollers, their rolling directions are opposed to each other, so that when the lubricating function lowers due to the deterioration or leak-out of grease sealed for lubrication of the cylindrical rollers, the frictional resistance increases at the engaging peripheral surface portions between the adjacent cylindrical rollers and such friction may generate a defective rolling. As a result, the hollow roller 2 is not rotated smoothly, and finally, burning caused by frictional heat occurs to an extent that the hollow roller cannot be rotated.